MUC5AC and acute respiratory distress syndrome: In the ARDS animal model, type II alveolar epithelial intracellular stress is regulated by inducing abnormal mucin expression (Hancock et al., 2018), increased endoplasmic reticulum (ER) stress (Lawson et al., 2011), induce local tissue hypoxia (Xi et al., 2017; Burman et al., 2018), impairing the normal repair process and aggravating the fibrotic response (Michalski et al., 2022).